Lithium-ion battery and apparatus

ABSTRACT

This application provides a lithium-ion battery and an apparatus. The lithium-ion battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. A positive active material of the positive electrode plate includes Li x1 Co y1 M 1-y1 O 2-z1 Q z1 , where 0.5≤x1≤1.2, 0.8≤y1≤1.0, 0≤z1≤0.1, M is selected from one or more of Al, Ti, Zr, Y, and Mg, and Q is selected from one or more of F, Cl, and S. The electrolyte contains an additive A that is a polynitrile six-membered nitrogen-heterocyclic compound with a relatively low oxidation potential. The lithium-ion battery has superb cycle performance and storage performance, especially under high-temperature and high-voltage conditions.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Stage of International Application No.PCT/CN2019/125310, filed on Dec. 13, 2019, which claims priority toChinese Patent Application No. 201811535449.2, filed on Dec. 14, 2018,both of which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

This application relates to the field of energy storage materials, andin particular, to a lithium-ion battery and an apparatus.

BACKGROUND

Lithium-ion batteries are widely applied to electromobiles and consumerelectronic products due to their advantages such as high energy density,high output power, long cycle life, and low environmental pollution.Current requirements on lithium-ion batteries are high voltage, highpower, long cycle life, long storage life, and superb safetyperformance.

Currently, LiCoO₂ is widely used as a positive active material inlithium-ion batteries and shows relatively stable performance duringcycling between fully discharged LiCoO₂ and semi-charged Li_(0.5)CoO₂(4.2 V vs. Li). Therefore, lithium ions that are actually used accountonly for ½ of lithium ions actually contained in LiCoO₂. When thevoltage is greater than 4.2 V, the remaining ½ of lithium ions containedin LiCoO₂ may continue to be extracted. However, during deepdelithiation, Co³⁺ is oxidized into quite unstable Co⁴⁺, which oxidizesan electrolyte together with surface oxygen that loses a large quantityof electrons. In this case, a large amount of gas is produced inside thebatteries, causing the batteries to swell. In addition, due to acorrosive effect of HF in the electrolyte on a surface of a positiveelectrode, Co⁴⁺ is dissolved in the electrolyte and deposited on asurface of a negative electrode, catalyzing reduction of theelectrolyte, and also producing a large amount of gas that causes thebatteries to swell. In addition, due to high overlapping between a 3denergy level of Co and a 2p energy level of O, the deep delithiationalso causes lattice oxygen to lose a large quantity of electrons,resulting in sharp shrinkage of LiCoO₂ unit cells along a c-axisdirection, and leading to instability or even collapse of a local bulkstructure. This eventually causes loss of LiCoO₂ active sites, and arapid decrease in capacity of the lithium-ion batteries. Therefore,LiCoO₂ has very poor performance when being used in a high-voltagesystem greater than 4.2 V.

In view of this, this application is hereby proposed.

SUMMARY

In view of the problems in the background, an objective of thisapplication is to provide a lithium-ion battery and an apparatus. Thelithium-ion battery has superb cycle performance and storageperformance, especially under high-temperature and high-voltageconditions.

To achieve the foregoing objective, according to a first aspect, thisapplication provides a lithium-ion battery, including an electrodeassembly and an electrolyte, wherein the electrode assembly includes apositive electrode plate, a negative electrode plate, and a separator. Apositive active material of the positive electrode plate includesL_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1), where 0.5≤x1≤1.2, 0.8≤y1≤1.0,0≤z1≤0.1, M is selected from one or more of Al, Ti, Zr, Y, and Mg, and Qis selected from one or more of F, Cl, and S. The electrolyte containsan additive A that is selected from one or more of compounds representedby Formula I-1, Formula I-2, and Formula I-3. In the Formula I-1, theFormula I-2, and the Formula I-3, R₁, R₂, R₃, and R₄ each areindependently selected from a hydrogen atom, a halogen atom, asubstituted or unsubstituted C₁-C₁₂ alkyl group, a substituted orunsubstituted C₁-C₁₂ alkoxy group, a substituted or unsubstituted C₁-C₁₂amine group, a substituted or unsubstituted C₂-C₁₂ alkenyl group, asubstituted or unsubstituted C₂-C₁₂ alkynyl group, a substituted orunsubstituted C₆-C₂₆ aryl group, or a substituted or unsubstitutedC₂-C₁₂ heterocyclic group, where a substituent group is selected fromone or more of a halogen atom, a nitrile group, a C₁-C₆ alkyl group, aC₂-C₆ alkenyl group, and a C₁-C₆ alkoxy group; x, y, and z each areindependently selected from integers 0-8; and m, n, and k each areindependently selected from integers 0-2.

According to a second aspect of this application, this applicationprovides an apparatus, including the lithium-ion battery as described inthe first aspect of this application.

Compared with the prior art, this application provides at least thefollowing beneficial effects: In this application, a positive activematerial that contains a metal ion M-doped lithium cobalt oxide materialLi_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1) is used, where the doping element Mserves as a framework in the lithium cobalt oxide material. This couldreduce lattice deformation of the lithium cobalt oxide material duringdeep delithiation, delay degradation of bulk structure of the lithiumcobalt oxide material, and improve structural stability of thelithium-ion battery when the lithium-ion battery is used at a highvoltage greater than 4.2 V. The electrolyte used in this applicationalso contains a polynitrile six-membered nitrogen-heterocyclic compoundwith a relatively low oxidation potential, such that a stable complexlayer can be formed on a surface of the positive active material duringformation of the battery. This could effectively passivate the surfaceof the positive active material, reduce surface activity of the positiveactive material, and suppress dissolution of a transition metal(especially cobalt) into the electrolyte, thereby reducing gasproduction of the battery while reducing side reactions. Therefore, thelithium-ion battery of this application has superb cycle performance andstorage performance, especially under high-temperature and high-voltageconditions. The apparatus of this application includes the lithium-ionbattery as described in the first aspect of this application, andtherefore provides at least the same advantages as the lithium-ionbattery.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows carbon nuclear magnetic resonance spectroscopy of acompound A1.

FIG. 2 shows carbon nuclear magnetic resonance spectroscopy of acompound A2.

FIG. 3 shows carbon nuclear magnetic resonance spectroscopy of acompound A3.

FIG. 4 is a schematic diagram of an embodiment of a lithium-ion battery.

FIG. 5 is a schematic diagram of an embodiment of a battery module.

FIG. 6 is a schematic diagram of an embodiment of a battery pack;

FIG. 7 is an exploded diagram of FIG. 6.

FIG. 8 is a schematic diagram of an embodiment of an apparatus using alithium-ion battery as a power source.

Reference numerals in the accompanying drawings are described asfollows:

-   -   1. battery pack;    -   2. upper cabinet body;    -   3. lower cabinet body;    -   4. battery module; and    -   5. lithium-ion battery.

DESCRIPTION OF EMBODIMENTS

The following describes in detail the lithium-ion battery and apparatusaccording to this application.

A lithium-ion battery according to a first aspect of this application isdescribed first.

The lithium-ion battery according to this application includes anelectrode assembly and an electrolyte. The electrode assembly includes apositive electrode plate, a negative electrode plate, and a separator.

A positive active material of the positive electrode plate includesLi_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1), where 0.5≤x1≤1.2, 0.8≤y1≤1.0,0≤z1≤0.1, M is selected from one or more of A1, Ti, Zr, Y, and Mg, and Qis selected from one or more of F, Cl, and S. The electrolyte containsan additive A that is selected from one or more of compounds representedby Formula I-1, Formula I-2, and Formula I-3.

In the Formula I-1, the Formula I-2, and the Formula I-3, R₁, R₂, R₃,and R₄ each are independently selected from a hydrogen atom, a halogenatom, a substituted or unsubstituted C₁-C₁₂ alkyl group, a substitutedor unsubstituted C₁-C₁₂ alkoxy group, a substituted or unsubstitutedC₁-C₁₂ amine group, a substituted or unsubstituted C₂-C₁₂ alkenyl group,a substituted or unsubstituted C₂-C₁₂ alkynyl group, a substituted orunsubstituted C₆-C₂₆ aryl group, or a substituted or unsubstitutedC₂-C₁₂ heterocyclic group, where a substituent group (indicating asubstitution case in the “substituted or unsubstituted” mentioned inthis application) is selected from one or more of a halogen atom, anitrile group, a C₁-C₆ alkyl group, a C₂-C₆ alkenyl group, and a C₁-C₆alkoxy group; x, y, and z each are independently selected from integers0-8; and m, n, and k each are independently selected from integers 0-2.

The lithium-ion battery of this application has superb cycle performanceand storage performance, especially under high-temperature andhigh-voltage conditions.

Details are as follows:

(1) In this application, a positive active material that contains ametal ion M-doped lithium cobalt oxide materialLi_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1) is used, where the doping element Mserves as a framework in the lithium cobalt oxide material. This couldreduce lattice deformation of the lithium cobalt oxide material duringdeep delithiation, delay degradation of bulk structure of the lithiumcobalt oxide material, and improve structural stability of thelithium-ion battery when the lithium-ion battery is used at a highvoltage greater than 4.2 V.

(2) The additive A contained in the electrolyte in this application is apolynitrile six-membered nitrogen-heterocyclic compound with arelatively low oxidation potential. Nitrogen atoms in the nitrile groupscontain lone pair electrons, which have relatively strong complexationwith a transition metal in the positive active material. After beingapplied in the electrolyte, the additive A may be adsorbed on a surfaceof the positive active material during formation of the battery to forma loose and porous complex layer and effectively passivate the surfaceof the positive active material. The complex layer could avoid directcontact between the surface of the positive active material and theelectrolyte and reduce surface activity of the positive active material,and could further reduce a large quantity of side reactions on thesurface of the positive active material and suppress dissolution of atransition metal (especially cobalt) into the electrolyte. Therefore,the electrolyte in this application may have an effect of reducing sidereaction products and reducing gas production.

(3) The additive A in this application has a special six-memberednitrogen-heterocyclic structure. A spacing between nitrile groups iscloser to that between transition metals on the surface of the positiveactive material. This could maximize complexation of the nitrile groupsand allow more nitrile groups to have a complexation effect. Therefore,compared with a conventional linear nitrile compound, the polynitrilesix-membered nitrogen-heterocyclic compound in this application has abetter passivation effect.

(4) The special six-membered nitrogen-heterocyclic structure of theadditive A in this application can further lower an oxidation potentialof molecules, so that a stable complex layer may be formed on thesurface of the positive active material during formation of the battery.This may help improve electrochemical performance of an entire batterysystem, for example, by reducing gas production and extending a cyclelife under high-temperature and high-voltage conditions.

In the lithium-ion battery of this application, preferably, based ontotal mass of the electrolyte, mass percent of the additive A is0.1%-10%. If the amount of the additive A is too low, improvement madeby the additive A to the electrolyte is not obvious; if the amount ofthe additive A is too high, the complex layer formed by the additive Abeing adsorbed on the surface of the positive active material would betoo thick and dense, affecting diffusion and migration of lithium ions,and greatly increasing positive electrode impedance. In addition,excessively high amount of the additive A further causes an increase inoverall viscosity of the electrolyte and a decrease in an ionicconductivity, and therefore, affects performance of the lithium-ionbattery. Preferably, an upper limit of the amount of the additive A maybe any one selected from 10%, 9%, 8%, 7%, 6%, 5%, 4.5%, 4%, 3.5%, 3%,2.5%, 2%, 1.5%, 1%, or 0.8%, and a lower limit of the amount of theadditive A may be any one selected from 0.1%, 0.2%, 0.3%, 0.4%, 0.5%,0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or 1.2%.

More preferably, based on the total mass of the electrolyte, the masspercent of the additive A is 0.1%-6%. Even more preferably, based on thetotal mass of the electrolyte, the mass percent of the additive A is0.1%-3.5%.

In an embodiment of the lithium-ion battery of this application, theelectrolyte may further contain an additive B that is LiBF₄. In ahigh-voltage lithium-ion battery system, a positive active materialeasily releases oxygen, and atoms B in LiBF₄ can stabilize oxygen atomsin the positive active material and have an effect of suppressing oxygenrelease of the positive active material, thus contributing to extensionof a life, especially a storage life, of the high-voltage lithium-ionbattery system.

Preferably, based on total mass of the electrolyte, mass percent of theadditive B is 0.1%-10%. More preferably, based on the total mass of theelectrolyte, the mass percent of the additive B is 0.1%-5%.

In another embodiment of the lithium-ion battery of this application,the electrolyte may further contain an additive C that is selected fromone or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC),and 1,3-propane sultone (PS). The additive C may further form, onsurfaces of positive and negative electrodes, a surface film containingone or more of double bonds, fluorine atoms, and sulfonate groups. Thesurface film has good chemical, electrochemical, mechanical, and thermalstability, and can avoid direct contact between the electrolyte and thesurfaces of the positive and negative electrodes while smoothlyconducting lithium ions, thereby providing an effect of suppressingoxidation and reduction side reactions on the surfaces of the positiveand negative electrodes. Therefore, this may significantly suppress gasproduction of the battery, and improve a cycle life and a storage lifeof a high-voltage lithium-ion battery system.

Preferably, based on total mass of the electrolyte, mass percent of theadditive C is 0.1%-10%. More preferably, based on the total mass of theelectrolyte, the mass percent of the additive C is 0.1%-5%.

In still another embodiment of the lithium-ion battery of thisapplication, the electrolyte may further contain both an additive B andan additive C. Preferably, based on total mass of the electrolyte, masspercents of the additive B and the additive C are independently0.1%-10%.

In the lithium-ion battery of this application, the electrolyte furtherincludes an organic solvent and a lithium salt.

The organic solvent used in the electrolyte in an embodiment of thisapplication may include a cyclic carbonate and a chain carbonate, andcould further improve cycle performance and storage performance of thelithium-ion battery under high-temperature and high-voltage conditions.In addition, it is easy to adjust a conductivity of the electrolyte to asuitable range, thus further helping the additives achieve a betterfilm-forming effect.

The organic solvent used in the electrolyte in an embodiment of thisapplication may further include a carboxylic acid ester. To be specific,the organic solvent in this application may include a mixture of acyclic carbonate, a chain carbonate, and a carboxylic acid ester. Thecarboxylic acid ester is characterized by large dielectric constant andlow viscosity, and could effectively prevent association of lithium ionsand anions in the electrolyte. In addition, the carboxylic acid ester ismore advantageous than the cyclic carbonate and the chain carbonate interms of ion conduction. Especially at low temperature, the carboxylicacid ester could ensure good ion conduction for the electrolyte.

Based on total mass of the organic solvent, mass percent of the cycliccarbonate may be 15%-55%, preferably 25%-50%; mass percent of the chaincarbonate may be 15%-74%, preferably, 25%-70%; and mass percent of thecarboxylic acid ester may be 0.1%-70%, preferably, 5%-50%.

Specifically, the cyclic carbonate may be selected from one or more ofan ethylene carbonate, a propylene carbonate, a 1,2-butylene carbonate,and a 2,3-butanediol carbonate. More preferably, the cyclic carbonatemay be selected from one or more of an ethylene carbonate and apropylene carbonate.

Specifically, the chain carbonate may be one or more asymmetric chaincarbonates selected from an ethyl methyl carbonate, a methyl propylcarbonate, a methyl isopropyl carbonate, a methyl butyl carbonate, andan ethyl propyl carbonate; the chain carbonate may also be one or moresymmetric chain carbonates selected from a dimethyl carbonate, a diethylcarbonate, a dipropyl carbonate, and a dibutyl carbonate; the chaincarbonate may also be a mixture of the asymmetric chain carbonate andthe symmetric chain carbonate.

Specifically, the carboxylic acid ester may be selected from one or moreof methyl pivalate, ethyl pivalate, propyl pivalate, butyl pivalate,methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, methylpropionate, ethyl propionate, propyl propionate, butyl propionate,methyl acetate, ethyl acetate, propyl acetate, and butyl acetate.

The lithium salt used in the electrolyte in an embodiment of thisapplication may be selected from one or more of LiPF₆, LiPO₂F₂, Li₂PO₃F,LiSO₃F, lithium trifluoro((methanesulfonyl)oxy)borate, LiN(SO₂F)₂,LiN(SO₂CF₃)₂, LiN(SO₂C₂F₅)₂, lithium bis[oxalate-O,O′] borate,difluorobis[oxalate-O,O′] lithium phosphate, andtetrafluoro[oxalate-O,O′] lithium phosphate.

In the lithium-on battery of this application, concentration of thelithium salt is not particularly limited, and may be adjusted accordingto actual needs.

In the lithium-ion battery of this application, preferably, theconductivity at 25° C. of the electrolyte is 4 mS/cm-12 mS/cm.

In the lithium-ion battery of this application, a preparation method forthe electrolyte is not limited, and the electrolyte may be preparedaccording to a method for a conventional electrolyte.

In the lithium-ion battery of this application,Li_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1) may be specifically selected fromone or more of LiCo_(0.9)Zr_(0.1)O₂, LiCo_(0.9)Ti_(0.1)O₂,Li_(1.5)Co_(0.8)Mg_(0.2)O₂,Li_(1.01)Co_(0.98)Mg_(0.01)Ti_(0.005)Al_(0.005)O₂,Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1),Li_(1.1)Co_(0.95)Mg_(0.01)Zr_(0.01)Al_(0.03)O₂,Li_(1.04)Co_(0.95)Mg_(0.02)Zr_(0.03)O_(1.95)F_(0.05),Li_(1.06)Co_(0.96)Mg_(0.02)Ti_(0.02)O₂,Li_(1.08)Co_(0.97)Mg_(0.01)Zr_(0.01)Al_(0.01)O_(1.9)S_(0.1),Li_(1.09)Co_(0.98)Mg_(0.01)Ti_(0.005)Al_(0.005)O₂,Li_(1.085)Co_(0.98)Zr_(0.01)Ti_(0.005)Al_(0.005)O_(1.9)Cl_(0.1),Li_(1.03)Co_(0.96)Mg_(0.01)Zr_(0.01)Ti_(0.01)Al_(0.01)O₂,Li_(1.04)Co_(0.97)Zr_(0.01)Al_(0.02)O_(1.9)F_(0.1),Li_(1.07)Co_(0.97)Zr_(0.01)Ti_(0.01)Al_(0.01)O_(1.9)S_(0.1),Li_(1.02)Co_(0.96)Mg_(0.02)Zr_(0.015)Ti_(0.005)O_(1.9)S_(0.1),Li_(1.03)Co_(0.98)Ti_(0.01)Al_(0.01)O_(1.9)Cl_(0.1),Li_(1.05)C_(0.97)Mg_(0.01)Zr_(0.01)Al_(0.01)O_(1.9)Cl_(0.1),Li_(1.04)Co_(0.95)Zr_(0.02)Ti_(0.03)O_(1.9)F_(0.1),Li_(1.09)Co_(0.97)Mg_(0.02)Ti_(0.01)O_(1.95)F_(0.05),Li_(1.03)Co_(0.95)Mg_(0.03)Ti_(0.02)O_(1.9)S_(0.1), andLi_(1.04)Co_(0.97)Zr_(0.01)Ti_(0.01)Al_(0.01)O_(1.9)S_(0.1).

In the lithium-ion battery of this application, the positive activematerial may further include one or more of a lithium nickel oxide, alithium manganese oxide, a lithium nickel manganese oxide, a lithiumnickel cobalt manganese oxide, a lithium nickel cobalt aluminum oxide,and a compound obtained by adding another transition metal ornon-transition metal to any of the foregoing oxide.

In the lithium-ion battery of this application, a negative activematerial in the negative electrode plate may be soft carbon, hardcarbon, artificial graphite, natural graphite, silicon, silicon oxidecompound, silicon carbon composite, lithium titanate, a metal that canform an alloy with lithium, or the like. One type of these negativeactive materials may be used alone, or two or more types may be used incombination.

In the lithium-ion battery of this application, the positive electrodeplate further includes a binder and a conductive agent. A positiveslurry including the positive active material, the binder, and theconductive agent is applied onto a positive current collector, and thendried to give the positive electrode plate. Types and amounts of theconductive agent and the binder are not specifically limited, and may beselected according to actual needs. A type of the positive currentcollector is not specifically limited either, and may be selectedaccording to actual needs. Preferably, the positive current collectormay be an aluminum foil.

Likewise, the negative electrode plate further includes a binder and aconductive agent. A negative slurry containing the negative activematerial, the binder, and the conductive agent is applied onto anegative current collector, and then dried to give the negativeelectrode plate. Types and amounts of the conductive agent and thebinder are not specifically limited, and may be selected according toactual needs. A type of the negative current collector is notspecifically limited either, and may be selected according to actualneeds. Preferably, the positive current collector may be a copper foil.

In the lithium-ion battery of this application, the separator isdisposed between the positive electrode plate and the negative electrodeplate to have an effect of separation. A type of the separator is notspecifically limited, and the separator may be, but not limited to, anyseparator materials used in existing lithium-ion batteries, for example,polyethylene, polypropylene, polyvinylidene fluoride, and a multilayercomposite film thereof.

In the lithium-ion battery of this application, an end-of-charge voltageof the lithium-ion battery is not less than 4.2 V, that is, thelithium-ion battery may be used at a high voltage of not less than 4.2V. Preferably, the end-of-charge voltage of the lithium-ion battery isnot less than 4.35 V.

The lithium-ion battery of this application may be either a hard-shelllithium-ion battery or a soft-package lithium-ion battery. Preferably, ametal hard shell is used for the hard-shell lithium-ion battery.Preferably, a packaging bag is used as a battery housing of thesoft-package lithium-ion battery. The packaging bag typically includesan accommodating portion and a sealing portion. The accommodatingportion is configured to accommodate the electrode assembly and theelectrolyte, and the sealing portion is configured to seal the electrodeassembly and the electrolyte. This application achieves more significantimprovement on performance of the soft-package lithium-ion battery,because the soft-package lithium-ion battery per se is prone to swellingduring use, whereas this application could greatly reduce gas productionof the battery and prevent from shortening the life of the battery dueto the swelling of the soft-package lithium-ion battery.

In the lithium-ion battery of this application, in the compoundsrepresented by the Formula I-1, the Formula I-2, and the Formula I-3:

The C₁-C₁₂ alkyl group may be a chain alkyl group or a cyclic alkylgroup, and the chain alkyl group may be a linear alkyl group or abranched chain alkyl group. Hydrogen on a ring of the cyclic alkyl groupmay be further replaced by an alkyl group. A preferred lower limit ofthe quantity of carbon atoms in the C₁-C₁₂ alkyl group is 1, 2, 3, 4, or5, and a preferred upper limit is 3, 4, 5, 6, 8, 10, or 12. Preferably,a C₁-C₁₀ alkyl group is selected. More preferably, a C₁-C₆ chain alkylgroup or a C₃-C₈ cyclic alkyl group is selected. Furthermore preferably,a C₁-C₄ chain alkyl group or a C₅-C₇ cyclic alkyl group is selected.Examples of the C₁-C₁₂ alkyl group may specifically include a methylgroup, an ethyl group, an n-propyl group, isopropyl group, an n-butylgroup, an isobutyl group, a sec-butyl group, a tert-butyl group, ann-pentyl group, an isopentyl group, a neopentyl group, a hexyl group, a2-methyl-pentyl group, a 3-methyl-pentyl group, a 1,1,2-trimethyl-propylgroup, a 3,3-dimethyl-butyl group, a heptyl group, a 2-heptyl group, a3-heptyl group, a 2-methylhexyl group, a 3-methylhexyl group, anisoheptyl group, an octyl group, a nonyl group, and a decyl group.

When the aforementioned C₁-C₁₂ alkyl group contains oxygen atoms, theC₁-C₁₂ alkyl group may be a C₁-C₁₂ alkoxy group. Preferably, a C₁-C₁₀alkoxy group is selected. More preferably, a C₁-C₆ alkoxy group isselected. Furthermore preferably, a C₁-C₄ alkoxy group is selected.Examples of the C1-C12 alkoxy group may specifically include a methoxygroup, an ethoxy group, an n-propoxy group, an isopropoxy group, ann-butoxy group, a sec-butoxy group, a t-butoxy group, an n-pentyloxygroup, an isopentyloxy group, a cyclopentyloxy group, and acyclohexyloxy group.

The C₂-C₁₂ alkenyl group may be a cyclic alkenyl group or a chainalkenyl group, and the chain alkenyl group may be a linear alkenyl groupor a branched alkenyl group. In addition, preferably, the C₂-C₁₂ alkenylgroup has one double bond. A preferred lower limit of the quantity ofcarbon atoms in the C₂-C₁₂ alkenyl group is 2, 3, 4, or 5, and apreferred upper limit is 3, 4, 5, 6, 8, 10, or 12. Preferably, a C₂-C₁₀alkenyl group is selected. More preferably, a C₂-C₆ alkenyl group isselected. Furthermore preferably, a C₂-C₅ alkenyl group is selected.Examples of the C₂-C₁₂ alkenyl group may specifically include a vinylgroup, an allyl group, an isopropenyl group, a pentenyl group, acyclohexenyl group, a cycloheptenyl group, and a cyclooctenyl group.

The C₂-C₁₂ alkynyl group may be a cyclic alkynyl group or a chainalkynyl group, and the chain alkynyl group may be a linear alkynyl groupor a branched alkynyl group. In addition, preferably, the C₂-C₁₂ alkynylgroup has one triple bond. A preferred lower limit of the quantity ofcarbon atoms in the C₂-C₁₂ alkynyl group is 2, 3, 4, or 5, and apreferred upper limit is 3, 4, 5, 6, 8, 10, or 12. Preferably, a C₂-C₁₀alkynyl group is selected. More preferably, a C₂-C₆ alkynyl group isselected. Furthermore preferably, a C₂-C₅ alkynyl group is selected.Examples of the C₂-C₁₂ alkynyl group may specifically include an ethynylgroup, a propargyl group, an isopropynyl group, a pentynyl group, acyclohexynyl group, a cycloheptynyl group, and a cyclooctynyl group.

The C₁-C₁₂ amine group may be selected from

where R′ and R″ are selected from the C₁-C₁₂ alkyl group.

The C₆-C₂₆ aryl group may be a phenyl group, a phenylalkyl group, abiphenyl group, or a fused ring aromatic hydrocarbon group (for example,a naphthyl group, an anthracenyl group, or a phenanthrenyl group). Thebiphenyl group and the fused ring aromatic hydrocarbon group may befurther substituted with an alkyl group or an alkenyl group. Preferably,a C₆-C₁₆ aryl group is selected. More preferably, a C₆-C₁₄ aryl group isselected. Furthermore preferably, a C₆-C₉ aryl group is selected.Examples of the C₆-C₂₆ aryl group may specifically include a phenylgroup, a benzyl group, a biphenyl group, a p-tolyl group, an o-tolylgroup, an m-tolyl group, a naphthyl group, an anthracenyl group, and aphenanthryl group.

A hetero atom in the C₂-C₁₂ heterocyclic group may be selected from oneor more of oxygen, nitrogen, sulfur, phosphorus, and boron, and aheterocyclic ring may be an aliphatic heterocyclic ring or an aromaticheterocyclic ring. Preferably, a C₂-C₁₀ heterocyclic group is selected.More preferably, a C₂-C₇ heterocyclic group is selected. Furthermorepreferably, a five-membered aromatic heterocyclic ring, a six-memberedaromatic heterocyclic ring, and a benzo heterocyclic ring are selected.Examples of the C₂-C₁₂ heterocyclic group may specifically include anethylene oxide group, a propylene oxide group, an ethylene sulfidegroup, an aziridine group, a β-propiolactone group, a furyl group, athienyl group, a pyrrolyl group, a thiazolyl group, an imidazolyl group,a pyridyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinylgroup, an indolyl group, and a quinolinyl group.

The halogen atom used as a substituent group may be selected from one ormore of a fluorine atom, a chlorine atom, and a bromine atom.Preferably, the halogen atom is a fluorine atom.

(1) Specifically, the compound represented by the Formula I-1 is apolycyanopyrimidine compound.

In the Formula I-1:

Preferably, R₁, R₂, R₃, and R₄ each are independently selected from ahydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, asubstituted or unsubstituted C₁-C₆ linear or branched alkyl group, asubstituted or unsubstituted C₅-C₉ cyclic alkyl group, a substituted orunsubstituted C₁-C₆ alkoxy group, a substituted or unsubstituted C₁-C₆amine group, a substituted or unsubstituted C₂-C₆ alkenyl group, asubstituted or unsubstituted C₂-C₆ alkynyl group, a substituted orunsubstituted C₆-C₁₂ aryl group, or a substituted or unsubstitutedC₂-C₁₂ heterocyclic group. More preferably, R₁, R₂, R₃, and R₄ each areindependently selected from a hydrogen atom, a fluorine atom, a chlorineatom, a bromine atom, a substituted or unsubstituted C₁-C₃ linear orbranched alkyl group, a substituted or unsubstituted C₅-C₇ cyclic alkylgroup, a substituted or unsubstituted C₁-C₃ alkoxy group, a substitutedor unsubstituted C₁-C₃ amine group, a substituted or unsubstituted C₂-C₃alkenyl group, a substituted or unsubstituted C₂-C₃ alkynyl group, asubstituted or unsubstituted C₆-C₈ aryl group, or a substituted orunsubstituted C₂-C₇ heterocyclic group. The substituent group isselected from one or more of halogen atoms.

Preferably, x is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2.

Preferably, y is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2.

Preferably, m is selected from 1 or 2.

Preferably, n is selected from 1 or 2.

Preferably, R₁ and R₃ are same groups. More preferably, R₁, R₃, and R₄are all same groups.

Preferably, R₁ and R₃ are both hydrogen atoms. More preferably, R₁, R₃,and R₄ are all hydrogen atoms.

Preferably, R₁, R₂, R₃, and R₄ are all hydrogen atoms; or R₁, R₃, and R₄are all hydrogen atoms, and R₂ is selected from a fluorine atom, achlorine atom, a bromine atom, a substituted or unsubstituted C₁-C₆linear or branched alkyl group, or a substituted or unsubstituted C₁-C₆alkoxy group. The substituent group is selected from one or more ofhalogen atoms. Preferably, the substituent group is selected from afluorine atom.

Preferably, the compound represented by the Formula I-1 may bespecifically selected from one or more of the following compounds, butthis application is not limited thereto:

(2) Specifically, the compound represented by the Formula I-2 is apolynitrile piperazine compound.

In the Formula I-2:

Preferably, R₁, R₂, R₃, and R₄ each are independently selected from ahydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, asubstituted or unsubstituted C₁-C₆ linear or branched alkyl group, asubstituted or unsubstituted C₅-C₉ cyclic alkyl group, a substituted orunsubstituted C₁-C₆ alkoxy group, a substituted or unsubstituted C₁-C₆amine group, a substituted or unsubstituted C₂-C₆ alkenyl group, asubstituted or unsubstituted C₂-C₆ alkynyl group, a substituted orunsubstituted C₆-C₁₂ aryl group, or a substituted or unsubstitutedC₂-C₁₂ heterocyclic group. More preferably, R₁, R₂, R₃, and R₄ each areindependently selected from a hydrogen atom, a fluorine atom, a chlorineatom, a bromine atom, a substituted or unsubstituted C₁-C₃ linear orbranched alkyl group, a substituted or unsubstituted C₅-C₇ cyclic alkylgroup, a substituted or unsubstituted C₁-C₃ alkoxy group, a substitutedor unsubstituted C₂-C₃ amine group, a substituted or unsubstituted C₂-C₃alkenyl group, a substituted or unsubstituted C₂-C₃ alkynyl group, asubstituted or unsubstituted C₆-C₈ aryl group, or a substituted orunsubstituted C₂-C₇ heterocyclic group. The substituent group isselected from one or more of halogen atoms.

Preferably, x is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2.

Preferably, y is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2.

Preferably, m is selected from 1 or 2.

Preferably, n is selected from 1 or 2.

Preferably, at least two of R₁, R₂, R₃, and R₄ are same groups. Morepreferably, at least three of R₁, R₂, R₃, and R₄ are same groups.

Preferably, at least two of R₁, R₂, R₃, and R₄ are hydrogen atoms. Morepreferably, at least three of R₁, R₂, R₃, and R₄ are hydrogen atoms.

Preferably, R₁, R₂, R₃, and R₄ are all hydrogen atoms; or three of R₁,R₂, R₃, and R₄ are hydrogen atoms, and the remaining one is selectedfrom a fluorine atom, a chlorine atom, a bromine atom, a substituted orunsubstituted C₁-C₆ linear or branched alkyl group, or a substituted orunsubstituted C₁-C₆ alkoxy group. The substituent group is selected fromone or more of halogen atoms. Preferably, the substituent group isselected from a fluorine atom.

Preferably, the compound represented by the Formula I-2 may bespecifically selected from one or more of the following compounds, butthis application is not limited thereto:

(3) Specifically, the compound represented by the Formula I-3 is apolynitrile s-triazine compound.

In the Formula I-3:

Preferably, R₁, R₂, and R₃ each are independently selected from ahydrogen atom, a fluorine atom, a chlorine atom, a bromine atom, asubstituted or unsubstituted C₁-C₆ linear or branched alkyl group, asubstituted or unsubstituted C₅-C₉ cyclic alkyl group, a substituted orunsubstituted C₁-C₆ alkoxy group, a substituted or unsubstituted C₁-C₆amine group, a substituted or unsubstituted C₂-C₆ alkenyl group, asubstituted or unsubstituted C₂-C₆ alkynyl group, a substituted orunsubstituted C₆-C₁₂ aryl group, or a substituted or unsubstitutedC₂-C₁₂ heterocyclic group. More preferably, R₁, R₂, and R₃ each areindependently selected from a hydrogen atom, a fluorine atom, a chlorineatom, a bromine atom, a substituted or unsubstituted C₁-C₃ linear orbranched alkyl group, a substituted or unsubstituted C₅-C₇ cyclic alkylgroup, a substituted or unsubstituted C₁-C₃ alkoxy group, a substitutedor unsubstituted C₁-C₃ amine group, a substituted or unsubstituted C₂-C₃alkenyl group, a substituted or unsubstituted C₂-C₃ alkynyl group, asubstituted or unsubstituted C₆-C₈ aryl group, or a substituted orunsubstituted C₂-C₇ heterocyclic group. The substituent group isselected from one or more of halogen atoms.

Preferably, x is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2.

Preferably, y is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2.

Preferably, z is selected from integers 0-6; more preferably, isselected from integers 0-4; furthermore preferably, is selected from 0,1, or 2.

Preferably, m is selected from 1 or 2.

Preferably, n is selected from 1 or 2.

Preferably, k is selected from 1 or 2.

Preferably, at least two of R₁, R₂, and R₃ are same groups.

Preferably, at least two of R₁, R₂, and R₃ are hydrogen atoms.

Preferably, R₁, R₂, and R₃ are all hydrogen atoms; or two of R₁, R₂, andR₃ are hydrogen atoms, and the remaining one is selected from a fluorineatom, a chlorine atom, a bromine atom, a substituted or unsubstitutedC1-C6 linear or branched alkyl group, or a substituted or unsubstitutedC1-C6 alkoxy group. The substituent group is selected from one or moreof halogen atoms. Preferably, the substituent group is selected from afluorine atom.

Preferably, the compound represented by the Formula I-3 may bespecifically selected from one or more of the following compounds, butthis application is not limited thereto:

In the lithium-ion battery of this application, the additive A may besynthesized by using the following method.

(1) Preparation of the compound represented by the Formula I-1

A reaction scheme is as follows:

A specific preparation process includes the following steps:

Adding aqueous solution P-2 with a concentration of 30%-40% dropwise toa raw material P-1 within 20 min-60 min, with quickly stirring thesolution. After the dropwise addition is completed, quickly stirring thesolution for 15 h-30 h. Stirring the solution in an oil bath at 70°C.-90° C. under reflux for 3 h-5 h to obtain a colorless, fuming, andviscous liquid intermediate product I-1-1. Then adding K₂CO₃, KI, andanhydrous acetonitrile, and quickly stirring them to form a solid-liquidmixture. Quickly adding a raw material P-3 at 40° C.-60° C., thenstirring them for 10 h-20 h, and cooling the mixture to roomtemperature. Then performing separation and purification to obtain thecompound represented by the Formula I-1.

(2) Preparation of the compound represented by the Formula I-2

A reaction scheme is as follows:

A specific preparation process includes the following steps:

Mixing anhydrous sodium carbonate, a raw material P-4, and a rawmaterial P-3 in absolute ethanol, and stirring them for 2 h-5 h for areaction. Repeatedly washing with hot ethanol for a plurality of timesto obtain a crude product, and performing recrystallization to obtainthe compound represented by the Formula I-2.

(3) Preparation of the compound represented by the Formula I-3

A reaction scheme is as follows:

A specific preparation process includes the following steps:

Mixing anhydrous sodium carbonate, a raw material P-5, and a rawmaterial P-3 in absolute ethanol, and stirring them for 2 h-5 h for areaction. Repeatedly washing with hot ethanol for a plurality of timesto obtain a crude product, and performing recrystallization to obtainthe compound represented by the Formula I-3.

In some embodiments, the lithium-ion battery may include an outerpackage for encapsulating the positive electrode plate, the electrodeplate, and an electrolyte medium. In an example, the positive electrodeplate, the negative electrode plate, and the separator may be laminatedor wound to form an electrode assembly of a laminated structure or anelectrode assembly of a wound structure, and the electrode assembly isencapsulated in an outer package. The electrolyte medium may be anelectrolyte, which infiltrates in the electrode assembly. There may beone or more electrode assemblies in the lithium-ion battery, dependingon needs.

In some embodiments, the outer package of the lithium-ion battery may bea soft package, for example, a soft bag. A material of the soft packagemay be plastic, for example, may include one or more of polypropylenePP, polybutylene terephthalate PBT, polybutylene succinate PBS, and thelike. Alternatively, the outer package of the lithium-ion battery may bea hard shell, for example, an aluminum shell.

Shape of the lithium-ion battery in this application is not particularlylimited, and may be of a cylindrical, square, or any other shape. FIG. 4shows an example of a lithium-ion battery 5 of a square structure.

In some embodiments, lithium-ion batteries may be assembled into abattery module, and the battery module may include a plurality oflithium-ion batteries. A specific quantity may be adjusted based onapplication and capacity of the battery module.

FIG. 5 shows an example of a battery module 4. Referring to FIG. 5, inthe battery module 4, a plurality of lithium-ion batteries 5 may besequentially arranged along a length direction of the battery module 4;or certainly, may be arranged in any other manner. Further, theplurality of lithium-ion batteries 5 may be fixed by using fasteners.

Optionally, the battery module 4 may further include a housing with anaccommodating space, and the plurality of lithium-ion batteries 5 areaccommodated in the accommodating space.

In some embodiments, battery modules may be further assembled into abattery pack, and the quantity of battery modules included in thebattery pack may be adjusted based on application and capacity of thebattery pack.

FIG. 6 and FIG. 7 show an example of a battery pack 1. Referring to FIG.6 and FIG. 7, the battery pack 1 may include a battery cabinet and aplurality of battery modules 4 disposed in the battery cabinet. Thebattery cabinet includes an upper cabinet body 2 and a lower cabinetbody 3. The upper cabinet body 2 can cover the cabinet body 3 and forman enclosed space for accommodating the battery modules 4. The pluralityof battery modules 4 may be arranged in the battery cabinet in anymanner.

An apparatus according to a second aspect of this application isdescribed next.

A second aspect of this application provides an apparatus. The apparatusincludes the lithium-ion battery in the first aspect of thisapplication, and the lithium-ion battery supplies power to theapparatus. The apparatus may be, but not limited to, a mobile device(for example, a mobile phone or a notebook computer), an electricvehicle (for example, a full electric vehicle, a hybrid electricvehicle, a plug-in hybrid electric vehicle, an electric bicycle, anelectric scooter, an electric golf vehicle, or an electric truck), anelectric train, a ship, a satellite, an energy storage system, and thelike.

A lithium-ion battery, a battery module, or a battery pack may beselected for the apparatus according to requirements for using theapparatus.

FIG. 8 shows an example of an apparatus. The apparatus is a fullelectric vehicle, a hybrid electric vehicle, a plug-in hybrid electricvehicle, or the like. To meet a requirement of the apparatus for highpower and a high energy density of a lithium-ion battery, a battery packor a battery module may be used.

In another example, the apparatus may be a mobile phone, a tabletcomputer, a notebook computer, or the like. The apparatus is generallyrequired to be light and thin, and may use a lithium-ion battery as itspower source.

To make the objectives, technical solutions, and beneficial technicaleffects of this application clearer, this application is furtherdescribed below in detail with reference to embodiments. It should beunderstood that the embodiments described in this specification aremerely intended to explain this application, but not to limit thisapplication. Formulations, proportions, and the like of the embodimentsmay be adjusted according to local conditions without substantial effecton results.

All reagents, materials, and instruments that are used in Examples andComparative Examples are commercially available unless otherwisespecified. Specific synthesis processes of additives A1, A2, and A3 areas follows. Other types of additives A may be synthesized according tosimilar methods.

Synthesis of the Additive A1:

37% formaldehyde aqueous solution was added dropwise to1,3-propanediamine within 0.5 h with quick stirring. After thecompletion of dropwise addition, the solution was still quickly stirredfor 20 h. Then the solution was stirred in an oil bath at 80° C. refluxfor 4 h to obtain intermediate product hexahydropyrimidine as acolorless, fuming, and viscous liquid. K₂CO₃, KI, and anhydrousacetonitrile were added, followed by quick stirring to form asolid-liquid mixture. Then P-chloropropionitrile was added at 60° C.within 0.5 h. The mixture was stirred for 17 h, and cooled to roomtemperature. Then the mixture was subjected to separation andpurification to obtain A1. Carbon nuclear magnetic resonancespectroscopy was shown in FIG. 1.

Synthesis of the Additive A2:

Anhydrous sodium carbonate, piperazine, and P-chloropropionitrile weremixed in absolute ethanol, and stirred for 4 h for reaction. The mixturewas repeatedly washed with hot ethanol for a plurality of times toobtain a crude product, and subjected to recrystallization to obtain A2.Carbon nuclear magnetic resonance spectroscopy was shown in FIG. 2.

Synthesis of the Additive A3:

Anhydrous sodium carbonate, 1,3,5-s-triazine, and chloroacetonitrilewere mixed in absolute ethanol, and stirred for 4 h for reaction. Themixture was repeatedly washed with hot ethanol for a plurality of timesto obtain a crude product, and subjected to recrystallization to obtainA3. Carbon nuclear magnetic resonance spectroscopy was shown in FIG. 3.

In Examples 1-30 and reference Comparative Examples 1-2, lithium-ionbatteries was prepared according to the following method.

(1) Preparation of an Electrolyte

A mixed solution of ethylene carbonate (EC for short), ethyl methylcarbonate (EMC for short) and diethyl carbonate (DEC for short) was usedas an organic solvent, where a mass ratio of EC, EMC, and DEC was 1:1:1.LiPF₆ was used as a lithium salt in an amount of 12.5% relative to thetotal mass of the electrolyte. Additives were added according toelectrolyte composition as shown in Table 1, where percents of alladditive components are calculated relative to the total mass of theelectrolyte.

Additives A used in the Examples and Comparative Examples wereabbreviated as follows:

(2) Preparation of a Positive Electrode Plate

A positive active material, a binder PVDF, and a conductive agentacetylene black in Table 1 based on a mass ratio of 98:1:1 were mixed.N-methylpyrrolidone was added. The resulting mixture was stirred byusing a vacuum mixer until the mixture was stable and uniform, to obtaina positive slurry. The positive slurry was uniformly applied onto analuminum foil. The aluminum foil was dried at room temperature, andtransferred to a blast oven at 120° C. for 1 h.

Then the Aluminum Foil was Cold-Pressed and Cut to Obtain a PositiveElectrode Plate.

(3) Preparation of a negative electrode plate

A negative active material graphite, a conductive agent acetylene black,a thickening agent sodium carboxymethyl cellulose, and a binderstyrene-butadiene rubber based on a mass ratio of 97:1:1:1 were mixed.Deionized water was added. The resulting mixture was stirred by using avacuum mixer until the mixture was stable and uniform, to obtain anegative slurry. The negative slurry was uniformly applied onto a copperfoil. The copper foil was dried at room temperature, and transferred toa blast oven at 120° C. for 1 h. Then the copper foil was cold-pressedand cut to obtain a negative electrode plate.

(4) Preparation of a Lithium-Ion Battery

The positive electrode plate, the negative electrode plate, and aPP/PE/PP separator were wound to obtain an electrode assembly. Theelectrode assembly was placed into an aluminum-plastic film of apackaging bag, followed by injection of the electrolyte. Then aprocedure including sealing, standing, hot-pressing and cold-pressing,forming, gas exhausting, and capacity testing were performed to obtain alithium-ion battery.

TABLE 1 Parameters of Examples 1-30 and Comparative Examples 1-2Additive A Additive B Additive C Positive active material Type AmountType Amount Type Amount Example 1Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 0.1% // / / Example 2Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 1.0% // / / Example 3Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 2.0% // / / Example 4Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 3.5% // / / Example 5Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 6.0% // / / Example 6Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 8.0% // / / Example 7Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 10.0% / / / / Example 8 Li_(1.01)Co_(0.98)Mg_(0.01)Ti_(0.005)Al_(0.005)O₂ A22.0% / / / / Example 9 Li_(1.1)Co_(0.95)Mg_(0.01)Zr_(0.01)Al_(0.03)O₂ A32.0% / / / / Example 10Li_(1.04)Co_(0.95)Mg_(0.02)Zr_(0.03)O_(1.95)F_(0.05) A4 2.0% / / / /Example 11 Li_(1.08)Co_(0.97)Mg_(0.01)Zr_(0.01)Al_(0.01)O_(1.9)S_(0.1)A5 2.0% / / / / Example 12Li_(1.085)Co_(0.95)Zr_(0.01)Ti_(0.005)Al_(0.005)O_(1.9)Cl_(0.1) A6 2.0%/ / / / Example 13Li_(1.03)Co_(0.96)Mg_(0.01)Zr_(0.01)Ti_(0.01)Al_(0.01)O₂ A7 2.0% / / / /Example 14 Li_(1.06)Co_(0.96)Mg_(0.02)Ti_(0.02)O₂ A8 2.0% / / / /Example 15 Li_(1.09)Co_(0.98)Mg_(0.01)Ti_(0.005)Al_(0.005)O₂ A9 2.0% / // / Example 16 Li_(1.04)Co_(0.97)Zr_(0.01)Al_(0.02)O_(1.9)F_(0.1) A102.0% / / / / Example 17Li_(1.07)Co_(0.97)Zr_(0.01)Ti_(0.01)Al_(0.01)O_(1.9)S_(0.1) A11 2.0% / // / Example 18Li_(1.02)Co_(0.96)Mg_(0.02)Zr_(0.015)Ti_(0.005)O_(1.9)S_(0.1) A12 2.0% // / / Example 19 Li_(1.03)Co_(0.98)Ti_(0.01)Al_(0.01)O_(1.9)Cl_(0.1) A132.0% / / / / Example 20Li_(1.05)Co_(0.97)Mg_(0.01)Zr_(0.01)Al_(0.01)O_(1.9)Cl_(0.1) A14 2.0% // / / Example 21 Li_(1.04)Co_(0.95)Zr_(0.02)Ti_(0.03)O_(1.9)F_(0.1) A152.0% / / / / Example 22Li_(1.09)Co_(0.97)Mg_(0.02)Ti_(0.01)O_(1.95)F_(0.05) A16 2.0% / / / /Example 23 Li_(1.03)Co_(0.95)Mg_(0.03)Ti_(0.02)O_(1.9)S_(0.1) A17 2.0% // / / Example 24Li_(1.04)Co_(0.97)Zr_(0.01)Ti_(0.01)Al_(0.01)O_(1.9)S_(0.1) A18 2.0% / // / Example 25Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 2.0%LiBF₄ 2.0% / / Example 26Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A2 2.0%LiBF₄ 2.0% / / Example 27Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A3 2.0%LiBF₄ 2.0% / / Example 28Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A1 2.0% // VC 2.0% Example 29Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A2 2.0% // FEC 2.0% Example 30Li_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1) A3 2.0% // PS 2.0% Comparative LiCoO₂ / / / / / / Example 1 ComparativeLi_(1.05)Co_(0.98)Mg_(0.005)Zr_(0.005)Ti_(0.01)O_(1.9)F_(0.1)Adiponitrile 2.0% / / / / Example 2

Tests for lithium-ion battery are described below.

(1) Cycle Performance Test for a Lithium-Ion Battery at NormalTemperature and High Voltage

At 25° C., the lithium-ion battery is charged at a constant current of 1C until a voltage of 4.35 V is reached, further charged at a constantvoltage of 4.35 V until a current of 0.05 C is reached, and thendischarged at a constant current of 1 C until a voltage of 3.0 V isreached. This is a charge/discharge cycle process, and the obtaineddischarge capacity at this time is the discharge capacity at the firstcycle. A lithium-ion battery is subjected to charge/discharge testaccording to the foregoing method for 200 cycles, to determine adischarge capacity at the 200^(th) cycle.

Capacity retention rate (%) of the lithium-ion battery after 200cycles=(the discharge capacity of the lithium-ion battery after 200cycles/the discharge capacity of the lithium-ion battery at the firstcycle)×100%.

(2) Cycle Performance Test for a Lithium-Ion Battery UnderHigh-Temperature and High-Voltage Conditions

At 45° C., the lithium-ion battery is charged at a constant current of 1C until a voltage of 4.35 V is reached, further charged at a constantvoltage of 4.35 V until a current of 0.05 C is reached, and thendischarged at a constant current of 1 C until a voltage of 3.0 V isreached. This is a charge/discharge cycle process, and the obtaineddischarge capacity at this time is the discharge capacity at the firstcycle. A lithium-ion battery is subjected to charge/discharge testaccording to the foregoing method for 200 cycles, to determine adischarge capacity at the 200^(th) cycle.

Capacity retention rate (%) of a lithium-ion battery after 200cycles=(the discharge capacity of the lithium-ion battery after 200cycles/the discharge capacity of the lithium-ion battery at the firstcycle)×100%.

(3) Storage Performance Test for a Lithium-Ion Battery at HighTemperature

At 25° C., the lithium-ion battery is charged at a constant current of0.5 C until a voltage of 4.35 V is reached, and then charged at aconstant voltage of 4.35 V until a current of 0.05 C is reached. Thethickness of the lithium-ion battery is tested and denoted the thicknessas h₀. Then the lithium-ion battery is placed in a constant-temperaturebox at 85° C., stored for 24 h, and then taken out. Then the thicknessof the lithium-ion battery is tested again and denoted as h₁.

Thickness Expansion Rate (%) of the Lithium-Ion Battery after Storage at85° C. for 24 h=[(h ₁ −h ₀)/h ₀]×100%.

The lithium-ion batteries were tested in the above tests.

TABLE 2 Performance test results of Examples 1-30 and ComparativeExamples 1-2 Capacity retention Capacity retention Thickness rate afterrate after expansion 200 cycles 200 cycles rate at at 25° C./4.35 V at45° C./4.35 V 85° C./24 h Example 1 89% 82% 25%  Example 2 96% 92% 10% Example 3 98% 94% 5% Example 4 96% 91% 4% Example 5 93% 86% 2% Example 688% 79% 2% Example 7 83% 72% 1% Example 8 97% 93% 4% Example 9 96% 92%6% Example 10 98% 94% 8% Example 11 95% 91% 4% Example 12 95% 91% 5%Example 13 97% 93% 5% Example 14 95% 91% 6% Example 15 96% 92% 7%Example 16 96% 92% 4% Example 17 96% 92% 8% Example 18 98% 94% 9%Example 19 97% 93% 6% Example 20 96% 92% 7% Example 21 94% 90% 5%Example 22 98% 94% 3% Example 23 96% 92% 6% Example 24 97% 93% 4%Example 25 99% 96% 2% Example 26 98% 96% 3% Example 27 98% 95% 3%Example 28 97% 94% 6% Example 29 99% 96% 5% Example 30 96% 94% 4%Comparative 85% 78% 42%  Example 1 Comparative 89% 81% 14%  Example 2

It can be seen from comparisons between Examples 1-30 and ComparativeExamples 1-2 that the lithium-ion batteries of this application havesuper cycle performance and storage performance under high-temperatureand high-voltage conditions.

Compared with Comparative Example 1, in Examples of this application,the metal ion M-doped lithium cobalt oxide materialLi_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1) was used as the positive activematerial, and the additive A was used as an electrolyte additive. Thedoping element M served as a framework in the positive active material.This reduced lattice deformation of the positive active material duringdeep delithiation, delayed degradation of bulk structure of the positiveactive material, and greatly improved structural stability of thelithium-ion battery when the lithium-ion battery was used at highvoltage. The additive A was a polynitrile six-memberednitrogen-heterocyclic compound with a relatively low oxidationpotential, such that a stable complex layer was formed on a surface ofthe positive active material during formation of the battery. Thiseffectively passivated the surface of the positive active material,reduced surface activity of the positive active material, and avoideddirect contact between the electrolyte and the surface of the positiveactive material, thereby greatly reducing surface side reactions, andcorrespondingly reducing lithium ions consumed in the side reactions,and thus greatly decreasing a consumption rate of reversible lithiumions. The actual effect finally manifested was that capacity retentionrate of the lithium-ion battery after cycling was greatly increased. Dueto the production gas in some surface side reactions, the reduction ofsurface side reactions further indicated a decrease in gas production ofthe battery. The actual effect finally manifested was that thicknessexpansion of the lithium-ion battery was significantly reduced at hightemperature.

Compared with the linear nitrile compound used in Comparative Example 2,the polynitrile six-membered nitrogen-heterocyclic compound in Exampleshad a special six-membered nitrogen-heterocyclic structure with aspacing between nitrile groups closer to that between transition metalson the surface of the positive active material. This could maximizecomplexation of the nitrile groups and allow more nitrile groups to havea complexation effect. Therefore, the polynitrile six-memberednitrogen-heterocyclic compound in Examples had stronger coverage on atransition metal on the surface of the positive active material, betterpassivation on the surface of the positive active material, and alsooutstanding improvement on cycle performance and storage performance ofthe lithium-ion battery.

It can be further seen from Examples 1-7 that, when an end-of-chargevoltage was fixed at 4.35 V, with an increase (from 0.1% to 10%) in theamount of the additive A, the capacity retention rate of the lithium-ionbattery after cycling at 25° C. and 45° C. showed an ascent and thenshowed a decline trend, and the thickness expansion rate after storageat 85° C. for 24 h was decreasing. This was because when the amount ofthe additive A was relatively large, the complex layer formed by theadditive A being adsorbed on the surface of the positive active materialwas likely to be thicker and denser, affecting diffusion and migrationof lithium ions, and greatly increasing positive electrode impedance.Secondly, the additive A consumed lithium ions while forming the complexlayer, reducing lithium ions available for cycling. Finally, arelatively large amount of the additive A caused an increase in overallviscosity of the electrolyte and a decrease in an ionic conductivity, sothat the capacity retention rate of the lithium-ion battery aftercycling at 25° C. and 45° C. showed an ascent and then showed a declinetrend. Therefore, the amount of the additive A needs to be appropriate.Preferably, the amount is 0.1%-10%; more preferably, is 0.1%-6%;furthermore preferably, is 0.1%-3.5%.

Examples 25-27 studied the effect of LiBF₄ on the performance of thelithium-ion battery when the amount of the additive A was relativelypreferred. Compared with Example 3, in Examples 25-28, the thicknessexpansion rates after storage at 85° C. for 24 h were lower. This wasbecause atoms B in LiBF₄ stabilized oxygen atoms in the positive activematerial and had an effect of suppressing oxygen release of the positiveactive material. As a result, the lithium-ion battery showed betterstorage performance.

Examples 28-30 studied the effect of VC, FEC, and PS on the performanceof the lithium-ion battery when the amount of the additive A wasrelatively preferred. These additives helped form, on surfaces ofpositive and negative electrodes, a surface film containing doublebonds, fluorine atoms, or sulfonate groups. The surface film had goodchemical, electrochemical, mechanical, and thermal stability, and couldavoid direct contact between the electrolyte and the surfaces of thepositive and negative electrodes while smoothly conducting lithium ions,thereby providing an effect of suppressing oxidation and reduction sidereaction on the surfaces of the positive and negative electrodes.Therefore, adding the additives helps further improve the cycleperformance and the storage performance of the lithium-ion battery.

According to the disclosure and guidance in this specification, a personskilled in the art to which this application relates may also makeappropriate changes and modifications to the foregoing embodiments.Therefore, this application is not limited to the specific embodimentsdisclosed and described above, and modifications and changes to thisapplication shall also fall within the protection scope of the claims ofthis application. In addition, although some specific terms are used inthis specification, these terms are merely intended for ease ofdescription, and do not constitute any limitation on this application.

What is claimed is:
 1. A lithium-ion battery, comprising an electrodeassembly and an electrolyte, wherein the electrode assembly comprises apositive electrode plate, a negative electrode plate, and a separator,wherein a positive active material of the positive electrode platecomprises Li_(x1)Co_(y1)M_(1-y1)O_(2-z1)Q_(z1), wherein 0.5≤x1≤1.2,0.8≤y1≤1.0, 0≤z1≤0.1, M is selected from one or more of Al, Ti, Zr, Y,and Mg, and Q is selected from one or more of F, Cl, and S; theelectrolyte contains an additive A that is selected from one or more ofcompounds represented by Formula I-1, Formula I-2, and Formula I-3; and

in the Formula I-1, the Formula I-2, and the Formula I-3, R₁, R₂, R₃,and R₄ each are independently selected from a hydrogen atom, a halogenatom, a substituted or unsubstituted C1-C12 alkyl group, a substitutedor unsubstituted C1-C12 alkoxy group, a substituted or unsubstitutedC1-C12 amine group, a substituted or unsubstituted C2-C12 alkenyl group,a substituted or unsubstituted C2-C12 alkynyl group, a substituted orunsubstituted C6-C26 aryl group, or a substituted or unsubstitutedC2-C12 heterocyclic group, wherein a substituent group is selected fromone or more of a halogen atom, a nitrile group, a C1-C6 alkyl group, aC2-C6 alkenyl group, and a C1-C6 alkoxy group; x, y, and z each areindependently selected from integers 0-8; and m, n, and k each areindependently selected from integers 0-2.
 2. The lithium-ion batteryaccording to claim 1, wherein in the Formula I-1, the Formula I-2, andthe Formula I-3, R₁, R₂, R₃, and R₄ each are independently selected froma hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C3linear or branched alkyl group, a substituted or unsubstituted C5-C7cyclic alkyl group, a substituted or unsubstituted C1-C3 alkoxy group, asubstituted or unsubstituted C1-C3 amine group, a substituted orunsubstituted C2-C3 alkenyl group, a substituted or unsubstituted C2-C3alkynyl group, a substituted or unsubstituted C6-C8 aryl group, or asubstituted or unsubstituted C2-C7 heterocyclic group, wherein asubstituent group is selected from halogen atoms; x, y, and z each areindependently selected from 0, 1, or 2; and m, n, and k each areindependently selected from 1 or
 2. 3. The lithium-ion battery accordingto claim 1, wherein in the Formula I-1, R₁ and R₃ are same groups; inthe Formula I-2, at least two of R₁, R₂, R₃, and R₄ are same groups; andin the Formula I-3, at least two of R₁, R₂, and R₃ are same groups. 4.The lithium-ion battery according to claim 3, wherein in the FormulaI-1, R₁ and R₃ are both hydrogen atoms; in the Formula I-2, at least twoof R₁, R₂, R₃, and R₄ are hydrogen atoms; and in the Formula I-3, atleast two of R₁, R₂, and R₃ are hydrogen atoms.
 5. The lithium-ionbattery according to claim 1, wherein the additive A is selected fromone or more of the following compounds:


6. The lithium-ion battery according to claim 1, wherein based on totalmass of the electrolyte, mass percent of the additive A is 0.1%-10%. 7.The lithium-ion battery according to claim 1, wherein the electrolytefurther contains an additive B that is LiBF₄, and based on total mass ofthe electrolyte, mass percent of the additive B is 0.1%-10%.
 8. Thelithium-ion battery according to claim 1, wherein the electrolytefurther contains an additive C that is selected from one or more ofvinylene carbonate, fluoroethylene carbonate, and 1,3-propane sultone,and based on the total mass of the electrolyte, mass percent of theadditive C is 0.1%-10%.
 9. The lithium-ion battery according to claim 1,wherein the lithium-ion battery is a hard-shell lithium-ion battery or asoft-package lithium-ion battery.
 10. The lithium-ion battery accordingto claim 1, wherein an end-of-charge voltage of the lithium-ion batteryis not less than 4.2 V.
 11. An apparatus, comprising the lithium-ionbattery according to claim
 1. 12. The lithium-ion battery according toclaim 3, wherein in the Formula I-1, R₁, R₃, and R₄ are all same groups.13. The lithium-ion battery according to claim 3, wherein in the FormulaI-2, at least three of R₁, R₂, R₃, and R₄ are same groups.
 14. Thelithium-ion battery according to claim 4, wherein in the Formula I-1,R₁, R₃, and R₄ are all hydrogen atoms.
 15. The lithium-ion batteryaccording to claim 4, wherein in the Formula I-2, at least three of R₁,R₂, R₃, and R₄ are hydrogen atoms.
 16. The lithium-ion battery accordingto claim 1, wherein based on total mass of the electrolyte, mass percentof the additive A is 0.1%-6%.
 17. The lithium-ion battery according toclaim 1, wherein based on total mass of the electrolyte, mass percent ofthe additive A is 0.1%-3.5%.
 18. The lithium-ion battery according toclaim 7, wherein based on total mass of the electrolyte, mass percent ofthe additive B is 0.1%-5%.
 19. The lithium-ion battery according toclaim 8, wherein based on the total mass of the electrolyte, masspercent of the additive C is 0.1%-5%.
 20. The lithium-ion batteryaccording to claim 1, wherein an end-of-charge voltage of thelithium-ion battery is not less than 4.35 V.